The resignations of John Baldessari, Barbara Kruger and Catherine Opie from the Museum of Contemporary Arts board is a warning for an institution founded by artists.

Three of four artists on the Museum of Contemporary Art's board of trustees have now resigned. The dire action is a warning as much as a protest. It shows how trustees critically important to MOCA's future are being marginalized.

In commentary about the museum, a crucial fact of its widely celebrated, sometimes fractious history is often forgotten: MOCA was founded by artists. In 1979, a large and steadily expanding group around acclaimed abstract painter Sam Francis determined that it was long past time for a museum dedicated to the presentation and study of recent art. Soon they drew an influential array of civic leaders into their orbit.

Certainly no institution comes into being or grows into an entity of international stature without a host of important contributing parties. But artists reside at the core of MOCA's being. They're the soul inside what sometimes seems to be a soulless institutional life.

That central point has lately been driven home with clarity and precision through an extraordinary series of events. On Thursday, artist John Baldessari resigned from what had been MOCA's 36-member board. On Sunday a remarkable email sent to trustees by two distinguished artists, Barbara Kruger and Catherine Opie, was released. (It is reprinted in its entirety here.) They too have resigned from the board.

Their letter is shot through with deep insight and profound sorrow.

"We want the best for MOCA," the artists begin, framing their exit as a generous expression of faith that fellow board members share a common aim. The museum has been in turmoil since news broke nearly three weeks ago that MOCA's longtime chief curator Paul Schimmel had been fired along with other key staff. He was instrumental in building the institution's international reputation through what Kruger and Opie correctly characterize as "intellectually ambitious and visually compelling" programming.

News of the dismissal came as a sudden shock to much of the art audience — including many on the board, among them the artist-trustees. (That includes Ed Ruscha, who is out of the country but expressed dismay upon hearing the news.) MOCA's director, Jeffrey Deitch, has remained virtually silent. But Kruger and Opie were quick to downplay the distraction of clashing personalities, refocusing instead on principles.

The museum is unusual, though not unique, in having artists as trustees. Four are seated among the usual roster of business and civic leaders, philanthropists and art collectors. The accolade and responsibility of museum trusteeship is typically bestowed on those who make exceptional contributions — and that certainly applies to the four acclaimed Los Angeles artists who, until recent days, have been at MOCA.

Opie's first solo museum show of photographs was held there. Kruger's powerful agit-prop graphics were the subject of a 1999 retrospective. Painter Ruscha and Conceptual artist Baldessari have likewise had MOCA retrospectives. Artists' labor is at the top of the pyramid of effort that makes a museum worthwhile.

Together they also represent the era in which L.A. came into its own as a formidable artistic powerhouse. Ruscha emerged as a potent force in the 1960s, Baldessari in the 1970s, Kruger in the '80s and Opie in the '90s. That they were not consulted by board leadership about the ax falling on the staff's leading curator for the past 22 years demonstrates the degree to which crucial trustees have been set aside — and likely will continue to be. It is a breathtaking display of institutional dysfunction at the top.

Here's a sobering fact: Defective trustee leadership was also at the root of MOCA's much-publicized financial catastrophe nearly four years ago — a near-death experience from which the museum has struggled to recover ever since.

MOCA's professional staff was hardly blameless, but it's the trustees who hold final fiduciary responsibility. When the nation's economy was driven into a tailspin, the museum's fiscal house of cards collapsed. Discovery that operating endowments and restricted funds had been inappropriately spent down to pay expenses showed that MOCA's leadership had been playing a dangerous, irresponsible game.

Now, board leadership is in the hands of nonvoting MOCA life trustee Eli Broad, the financier who supposedly "rescued" the museum in 2008 through a $30-million pledge from his foundation. To observe that the board he commands, now down to 33 voting members, remains at least as defective as before is disheartening in the extreme.

"It has been an honor to serve on the board," Kruger and Opie wrote. "But now we wonder if our position [is] just symbolic and that our ability to be heard and to suggest and make change has become a kind of inconvenience to the instrumental workings of the board."

We should all be wondering exactly that.

A friend wrote to me about these awful events the other day, rephrasing T.S. Eliot: "Trustees come and go. Talking of Michelangelo." Swaggering vanities endure, while art is reduced to servitude.